Inflammatory Bowel Disease and Vaccines

1. What is Inflammatory Bowel Disease?

Inflammatory Bowel Disease, also known as IBD, is a
general medical term used to refer to chronic inflammatory diseases of the
intestine.

Two common inflammatory bowel diseases are ulcerative colitis and Crohn's
disease. These chronic illnesses can inflame the gastrointestinal tract
causing bloody diarrhea, abdominal pain, and weight loss. Ulcerative
colitis can affect the entire large intestine or the rectum. Crohn's
disease mainly affects short segments of both the small and large
intestine. Although IBD can begin at any age, it's usual onset is from age
15 to 30 years. IBD is a rare disease with 3-20 new cases recognized per
100,000 persons per year.

2. What causes inflammatory bowel disease?

The cause(s) of inflammatory bowel disease is not
known.

There are several unproven theories as to the cause(s) of IBD: A) IBD is
known to occur in the same family suggesting a possible inherited cause.
B) A possible environmental cause is suggested because Crohn's disease
most often occurs in people who smoke , residents of Northern European
countries and in urban areas. C) Another theory is that significant
emotional events in a persons life may trigger the disease. D) Other
researchers speculate that the disease may be caused by an infection or
virus. E) Still others believe that the body's immune system is reacting
to unidentified or unknown antigens (a protein marker on the surface of
cells that identifies the cell). This antigen would cause the immune
system to respond inappropriately resulting in chronic inflammation.

It is not known if measles, mumps or rubella virus infection can cause
IBD. The virus that causes measles disease infects the respiratory system
and then spreads to lymphatic tissue (an important part of our immune
system). During the acute infection, lymph cells in the gastrointestinal
(GI) tract are infected but whether this causes chronic inflammation is
highly questionable. One theory speculates that measles virus may persist
in the intestine in certain individuals and later trigger a chronic
inflammatory infection, however this has not been proven. Because MMR
vaccine contains a very weak live measles virus it has been suggested that
measles vaccine could cause an inflammatory process in the intestine. This
theory has not been proven and is speculative. Two types of data -
epidemiological and pathological-link measles infection and IBD. However,
because conflicting results have been obtained for both types of data by
different investigators, this link can not be established.

3. Does the measles virus vaccine cause IBD?

There is no scientific proof that measles vaccine
virus can cause IBD.

In fact, because almost everyone is vaccinated when they are young, most
people with IBD will have received a vaccine. In order to prove that
measles vaccine caused IBD it would be necessary to prove that the measles
virus is definitely present in GI lesions, that it is active, and that it
can cause an inflammatory response. Additionally, it would have to be
shown that this reaction was caused by the measles virus or by the
attenuated (weakened) measles vaccine virus.

4. What about studies that have suggested an association
between measles virus vaccine and IBD?

Isolated studies that have suggested an association
are weak and have several flaws.

The possibility of an association between measles
virus and chronic inflammatory bowel disease was recently discussed in a
British medical journal, The Lancet. Researchers believe they discovered a
new childhood illness that caused bowel disease and psychiatric problems
including behavioral disorders and autism. MMR vaccine was suggested as a
possible cause. The theory is that MMR vaccine could lead to intestinal
inflammation resulting in decreased absorption of the intestinal tract to
essential vitamins and nutrients which in turn could lead to developmental
disorders. An editorial expressing concerns about the study was also
published in the same issue. That all patients had bowel disease is not
surprising since all were referred to a department of gastroenterology.
Some of the concerns expressed were that in this small study (12 patients)
there is no report of detection of vaccine viruses in GI or brain tissue
for any of the patients. Multiple laboratories using more sensitive and
specific laboratory tests, have failed to detect any findings to suggest
this. In addition the GI pathology should have existed prior to the
behavioral symptoms to support there theory. The researchers reported the
onset of GI symptoms was unknown in 5 patients and noted after the onset
of behavioral symptoms in another 5 patients.

A few Swedish studies have also suggested a high risk of Crohn's Disease
in those exposed to measles in utero. However, the Swedish studies
involved very small numbers of cases, 2 cases in the first study and 4 in
the second study (2 of which were cases in the first study).

Another study suggested in a retrospective cohort study that MMR vaccine
might be a risk factor for Crohn's disease. However, the selection and
recall biases and the differences in data collection in this study were so
substantial as to cast doubt on the validity of the findings.

Another study has reported finding measles virus proteins and RNA in the
intestinal tissue of cases of Crohn's disease using in situ hybridization
and immunologic staining .

5. Is there scientific evidence (both epidemiologic and
laboratory) to show there is no association between measles vaccine and
inflammatory bowel disease?

There is strong scientific evidence (both
epidemiologic and laboratory) to show there is no association between
measles vaccine and inflammatory bowel disease.

In June 2000, the results of a population-based
epidemiologic study conducted by the CDC, concluded that there was no
evidence that vaccination with MMR or other measles-containing vaccines,
or the the age of vaccination early in life, was associated with an
increased risk for the the development of IBD. Using a case-control
design, the study compared patients diagnosed with IBD and those without
IBD, and looked at the vaccination history of MMR vaccine and the
timing of vaccinations. No association was found to link the MMR
vaccine and IBD. This study was the result of a collaborative
project between the CDC and four large HMO's, part of the Vaccine Safety
Datalink Project.

Four other epidemiologic studies have failed to confirm the possible
association between measles virus and inflammatory bowel disease. Nielsen
et al. examined all possible cases of measles in pregnant women admitted
to a Copenhagen hospital from 1915-1966. None of the offspring of the 25
identified women had developed Crohn's disease. In 1995, Hermon-Taylor
compared the incidence of Crohn's disease in England and Wales with
measles infection, including information after the introduction of measles
vaccine. No association was found. In their case-control studies, Jones et
al and Feeney et al found no association between IBD and measles infection
or measles vaccine, respectively.

In another study, researchers used the same laboratory methodology as
Wakefield et al., and could not identify any measles virus in patients
with IBD, although they did find the presence of other viral and bacterial
agents (Liu). Several other research groups using more sensitive and
specific tests (polymerase chain reaction, PCR) have not found any
evidence of measles virus RNA in the gastrointestinal tissues of patients
with Crohn's Disease or ulcerative colitis.

6. What does the CDC recommend for measles, mumps rubella
(MMR) vaccine?

The CDC continues to recommend two doses of MMR
vaccine for all persons; for children, the first dose is recommended at
12-15 months of age and the second dose is recommended at 4-6 years of
age.

Although the risk of Inflammatory Bowel Disease (IBD) is higher for those
who have relatives with IBD, there are no data to suggest that measles
vaccine will increase or decrease this risk. Measles vaccine is
recommended for children with a family history of IBD unless there is
another specific reason not to vaccinate. (for example, in persons who
very ill and are not able to fight infections)

Source: Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, November 2000